This thread is about an off-the-shelf GPS + 4GB storage device that is similar to the Parrot Flight Recorder, but costs Â£25 (30 euros) and is smaller. It does not require any hardware modification. However, be sure to read the limitations below.

navistick_4gb.jpg

First some history. Some months ago I found this device on the intertubes and bought it purely as a project for modifying the drone. This little stick helped figure out some details of the Flight Recorder before it had even been released, starting because I noticed that the 2.4.1 firmware update included the driver needed to run it and that the drone seemed to recognise it, and eventually culminating in pawelsky's DIY Flight Recorder. I would have posted this before Parrot's own device was even released, but unfortunately my drone died immediately before the final step so I never got to test it. That is, until today when my drone returned from repairs.

First some details about the hardware: it is a Navistick 4GB, distributed in the UK by Norcom and sold by Meridian Chartware. There is also a 2GB version available in the US for $35. Internally is a USB hub, CP2102 USB-serial converter, SirfStar III GPS chip, and a replaceable microSD card (so you could fit a bigger one if you wanted). The eagle-eyed amongst you will notice that although most of the components are exactly the same, the GPS chip is not the same as the SirfStar IV in the Parrot device. This is a previous generation GPS so it may beless sensitive/accurate, and it also has the same limitations as the Globalsat GPS used in pawelsky's mod - i.e. it updates at only 1Hz instead of 5Hz, and does not support all the commands that the drone asks for.

However, I have successfully flown the drone around my local park using the GPS navigation function without any significant hitches, and FreeFlight showed upto 8 satellites and a lock of 1m. I don't have a Flight Recorder and so it's hard to do comparisons, but it is by no means flawless. The drone sometimes seemed to stop moving towards its waypoint before it got there, even though the iPad showed the location on the map correctly. I think the accuracy shown in the top right corner also was going down (from 1m to 3m) at high speeds, which makes sense given the 1Hz update rate. To what degree the accuracy displayed by FreeFlight reflects the "real" accuracy of this device, is not known.

Showing accuracy:

image.jpg

Waiting for satellite lock:

image.jpg

Installed on the drone:

navistick_ardrone.jpeg

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WARNING: You will be making changes to the EEPROM configuration of your GPS device. You might cause irreparable damage to it. I can't be responsible if that happens.

1. Buy the device.
2. Install the Windows driver from Silicon Labs.
3. Check it is working normally!
4. Download the Customisation Utility from SiliconLabs (AN721SW.zip).
5. Use the utility to change the VID to 19CF and the PID to 3000. Pawelsky's thread has a screenshot - this process is the same as the DIY flight recorder.
6. Click "Program device" to make the change. After the change has been written, you should hear the USB device disconnect and reconnect. The utility may show an error after validation, it should be OK. I think this is because after writing the changes, the driver no longer recognises the GPS as a standard CP2102... because it is now a Flight Recorder!
7. (Optional) Install Parrot's flight recorder drivers. This should allow you to use it in Windows, e.g. with the apps that came with it. If you install them before step 5 it might prevent the error message, I'm not sure as I didn't do it in that order.
8. Go to a controlled environment where you can't lose your drone or injure anyone.
9. Connect to the drone (firmware 2.4.1 or later), power up and wait for a good lock (it might take a minute).
10. Fly!

I'm almost temped to give this a try to see how it compares with the Parrot FR - I've only ever seen an accuracy of 2m with FR.

Interesting. I got 1m with the drone just sitting on my car next to my house, not exactly clear skies. And then in the middle of the park of course. I found that while moving around it tends to be 2m or 3m.

By the way one thing I noticed after 2 batteries of flying around, the GPS and battery were quite hot... I reckon the sirf IV power consumption should be lower, so maybe the FR doesn't get as hot?

okayyyy.. I've just bit the bullet and ordered one.. it was only $29 + $6.50 shipping... I'm willing to gamble on it to save $100, lol.. thanks for this Kyrt! I hope I can follow those steps and get it working.. who knows when it'll get here though, I bet it'll still be shipped from Taiwan.

My Flight Recorder is 35 g (official spec says 31) and reduces flight time on standard battery by about two minutes and a half compared to a 7 g SanDisk USB drive. I guess they could have easily reduced weight by half if they removed the female USB port and velcro and used stick form factor with thinner plastic.

Think I will still do your mod, I have had all the bits for a while and I'm fairly sure it's better than this sirf III gps. Honestly I'm surprised it flew so well - might be a fluke though!

In the meantime I'm working on a mod that will allow to use any GPS (not only SiRF) as a Flight Recorder. Prototype I have does report the data to FF app. I'll try that in flight when I find some time.